The measurement of very low flow provides a real challenge in the flowmeter technology as many well known mechanical or electromagnetic principles employed in the design of the flowmeters become inoperative due to low magnitude in the effects thereof. At the present time, the very low flows are measured by the hot wire method or by a positive displacement pump. There are strong demands in chemical and pharmaceutical industries for a nonintrusive flowmeter that is capable of measuring fluid flows ranging from very low velocities to quite high velocity. The present day flowmeter technology does not have a nonintrusive flowmeter capable of measuring very low velocities of the fluid.